Method for producing flat blanks for aluminum cooking vessels



A. F. STRACK METHQD FOR PRODUCING FLAT BLANKS FOR ALUMINUM COOKING VESSELS Filed Oct. 3, 1935 FIG.

/////7 va I u V NENToR ALBERT FRlEDRICH STRACK ATTORNEY Patented May 31, 1938 UNITED STATES METHOD FOR PRODUCING FLAT BLANKS FOR ALUMINUM COOKING VESSELS Albert Friedrich sti-sek, Suresne, France Application October 3, 1935, Serial No. 43,437 In Germany October 11, 1934 production of aluminum vessels, such as saucepans, f'ying pans, kettles orthe like, in which the bottom of the vessel is furnished on the exterior with heat-accumulating projections, whilst the remaining parts of the vessel are flat on either side. The semi-manufactured product according to the invention, consists of a plate, which is preferably of circular form in plan, and is of such thickness as to make the same suitable for the subsequent production of the walls of the vessel by means of the usual tools in a stamping or pressing operation, and which is furnished over its central area on the one side with projections, such as studs or ribs, integral with the plate and increasing the heating surface thereof, and possesses about this central area, which forms later the bottom of the ves-` sel, a marginal portion of suitable width which is fiat on both sides.

The method of producing the semi-manufactured product consists in placing an aluminum plate, which is of considerably greater thickness than that ultimately possessed by the semimanufactured product, and has been raised to a temperature approaching as closely as possible the melting point of the metal, on to a die, which is furnished with recesses open towards the top for the formation of the projections,and forcing the material into the recesses of the die by means of a suitable drop hammer or tup, the material thus forged being extended laterally to form a ductile sheet.

To perform the forging operation as described it is necessary for the impact face of the tup to be somewhat roughened, as otherwise the frietional resistance would be too small as regards v the lateral extension of the material, and in consequence the material would take this path of smaller resistance instead of also penetrating into the die. The extent of the penetration into the die in relation to the latera'l extension of the material may be regulated by the extent to which the roughenlng of the tup is performed. At the same time. by reason of the. roughening of the tup, the formation of craters is prevented on the upper face of the material above the recesses in the die, as the frictional resistance produced by the roughened surface prevents the material from flowing into the recesses too quickly. The roughness of the surface of the material caused by the roughened face of the tup may be readily removed afterwards by suitable treatment.

The piece of work is released from the die by compressed air which after each stroke of 'the tup is introduced from below through a series of passages into the single recesses or pockets of the die and maintains the piece of work in a fioating condition until the next impact of the tup.

The means employed for carrying out the above process cohprise a steel block, at the centre of which there is fitt'ed flrmly the die proper having 'the recesses or pockets determining the shape of the projections, which recessescommunicate with each other by means of passages extending to the bottom of the die and grooves or channels in the said bottom. This system of passages is connected, through the steel block, with a feed passage through which there is supplied the compressed air for lifting the piece of work in the die.

The invention will be described more fully with reference to the accompanying drawing, in which Fig. 1 shows, partly in section, a form of embodiment of a semi-manufactured product according to the invention, in which the projections comprise several circularly disposed series of conical studs surrounded by a supporting ring.

Fig. 2 shows diagrammatically in two longithe fitting of this die preferably being per-` formed by previously heating the block 2, so that after cooling it constitutes one piece together with the die 3. The die 3 possesses conic'al recesses or pockets 4. which correspond in number, shape and location with the projectionsb to viewed from bebe formed on the piece of work and may be, for example. as shown in Fig. 1. The recesses or pockets 4 merge downwards into passages 6; which open out into the lower face of the die and are interconnected by means of annular and radial grooves The system of passages in the die 3 is connected by a plurality of passages 8 in the block 2 with the feed passage 9, which communicates with a compresed air source (not shown) for supplying compressed air to lift the piece of work in the die. The upper portions IO and ll of the oppositely disposed walls of the die 3 and block 2 respectively are so embodied that they permit of the formation of an annulus I! on the piece of work.

Prior to its treatment the aluminum plate is raised to a temperature which approaches as closely as possible to the melting point of the metal, but which at the same time is sufllciently below this point that the metal will not melt by reason of the additional heat generated by the forging process.

This mode of operation is based on recognition of the fact that the aluminum, when the temperature has been raised in this way as near as possible towards the melting point, is so malleable under impact that it may be forced to desired extent into the recesses or pockets to form the projections, and at the same time also extended laterally. The plate I is accordingly acted upon by a drop hammer, the tup of which possesses a sufficiently large and suitably striated or otherwise roughened surface, so that with the means illustrated in Fig. 2 there is produced the semi-manufactured product according to Fig. 1.

The apertures I 3 in the annulus !2 necessary for passage of thecombustlon gases from the furnace are bored or punched afterwards.

The lifting of the piece of work in the die takes place by the free application of a compressed' air connection to the mouth of the passage 9. This method of application is important insofar as a fixed connection on the block would not be able to withstand the heavy and repeated blows of the hammer.

The lifting of the work by compressed air, in which connection the piece of work is lifted together with the weight of the hammer resting thereon, so that an even ejection takes place without deformation also in those cases in which the work may not be located perfectly evenly in the die, also offers the additional advantage that the air thoroughly cleans the passages and the recesses after the piece of work has been removed.

Moreover it is also important to lift the work after each blow of the hammer, as in this way the inherent force of acceleration is increased upon the next impact owing to the co-operation 'of the piece of work, which is caused to float by the compressed air, under its own weight. An important advantage also consists in the fact that contact between the pieces of work and the heat-dissipating surfaces of the: die 2 is avoided between each two strokes of thehammer, an undue cooling of the work thus being prevented.

What I claim as new and d'esire to secure by Letters Patent is:

1. A method of producing a flat blank for an aluminum cooking vessel having the bottom portion of the vessel finished in the blank and the side wall material adjacent thereto, comprising placlng a heated aluminum plate, which is of greater thickness and smaller diameter than the finished blank, on a block having a die therein corresponding to' the bottom portion, and repeatedly subjecting the plate to forging blows by a forging tool at thesame time lifting the plate from the block between each of the forging blows until the plate is forged to the desired dlameter to include the side wall material of the finished vessel and the bottom portion has received the desired conguration corresponding to that in the die, said forging step being carried out by the application of a varying frictional resistance in order to regulate the ratio between the displacement of the metal to form the desired configuraton of the bottom portion and the lateral extension of the side wall material.

2. A' method of producing a flat blank for an aluminum cooking vessel having the bottom portion of the vessel finished in the blank and the side wall material adjacent thereto, comprising placlng a heated aluminum plate, which is of greater thickness and smaller diameter than the finished blank, on a block having a die therein correspondingto the bottom portion, and repeatedly subjecting the plate to forging blows by a torging tool andf applying air under pressure below the plate in order to lift the plate from the die immediately following each forging blow until the plate is forged to the desired diameter to include the side wall material of the finished vessel and the bottom portion has received the desired coniiguration corresponding to that in the die.

3. A method of producing a flat blank for an aluminum cooking vessel having the bottom portion of the vessel finished in the blank and the side wall material adjacent thereto, comprising placing a heated aluminum plate, which is or greater thickness and smaller diameter than the finished blank. on a block having a die therein corresponding to the bottom portion, and repeatedly subjecting the plate to forging blows by a forging tool and forcing air under pressure between the plate and the block in order to lift said plate together with the forging tool immediately following each forging blow until the plate is i'orged to the desired diameter to include the. side wall material of the finished vessel and the bottom portion has received the desired con-- figuration corresponding to that in the die.

4. A method 'of producing a flat blank for an aluminum cooking vessel having the bottom portion of the vessel finished in the blank and the forging blows until the plate is forged to thedesired diameter to include the side wall material of the finished vessel and the bottom portion has received the desired configuration correspond'ng to that in the die in which projections are produced on said plate at the points of the perforations in the said die.

ALBERT FRIEDRICH STRACK. 

